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Saia-Burgess Controls AG
A.2.2
RS-485 / 422
Signals to RS-485 (RS-422)
5V
4V
3V
2.5V
2V
1V
0V
V
=
OZ
V
=
OH
V
=
OL
In the idle state, RS-422 is in the "mark" position
RS-422:
Signal type
Data signal
Control /
message signal
RS-485:
Signal type
Data signal
Not all manufacturers use the same connection configuration, so the data lines may
need to be crossed
To guarantee error-free operation of an RS-485 network, the network should be
terminated at both ends. Cable and line termination resistors should be selected in
accordance with manual 26 / 7 40 "Installation components for RS-485 networks".
Manual Manual PCD 1 / PCD 2 Series │ D ocument 26 / 737 EN22 │ 2 013-11-26
not active
mark
= mark
/TX
TX
0.9 V min ... 1.7 V
2 V min (with load) ... 5 V max (without load)
-2 V ... -5 V
Logical state
0 (space)
1 (mark)
0 (off)
1 (on)
Logical state
0 (space)
1 (mark)
Definitions of serial interfaces
space
e.g. Startbit
Polarity
TX positive to / T X
/ T X positive to TX
/ R TS positive to RTS
RTS positive to / R TS
Polarity
RX-TX positive to / R X- / T X
/ R X- / T X positive to RX-TX
Appendix
A
A-3
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